class Solution {
    public int findTargetSumWays(int[] nums, int target) {
        int n = nums.length;
        int sum = 0;
        for(int i = 0; i < n; i++) sum += nums[i];
        int aim = (sum + target) / 2;
        if(aim < 0 || (sum + target) % 2 == 1) return 0;
        // 状态表示 - nums [0, i] 区间选取元素，能够凑成 j 的方法数
        int[][] dp = new int[n + 1][aim + 1];
        dp[0][0] = 1;
        for(int i = 1; i <= n; i++){
            for(int j = 0; j <= aim; j++){
                dp[i][j] = dp[i - 1][j];
                if(j >= nums[i - 1]) dp[i][j] += dp[i - 1][j - nums[i - 1]];
            }
        }
        return dp[n][aim];
    }
}